Binocular interaction will be studied by extracellular single unit recording in the visual cortex of normal cats and in those that have been reared with strabismus or monocular deprivation. Binocular interaction will also be investigated psychophysically in normal human subjects and those with a history of strabismus or amblyopia or both. There are four principal objectives: (1) To compare stimulus specificity of right and left receptive fields of binocular cortical cells. Qualitative observations susggest that the two eyes are well matched. Experiments are proposed to determine this quantitatively for normal and for strabismic cats to see if there are differences between deviated and non-deviated eyes and between convergent and divergent conditions. (2) To study types and extent of binocular interaction for stimuli which are optimal and matched for the two eyes. For normal cats sinusoidal gratings will be presented dichoptically with one phase-shifted with respect to the other, while responses are recorded from cells in the visual cortex. Response patterns involving phase-specific and non-specific facilitation and suppression will be studied to determine the organization of binocular receptive fields. In addition, these patterns will be compared with those from bar stimuli to test the hypothesis that disparity and spatial frequency tuning are correlated. Dichoptically presented matched stimuli (gratings) will also be used to study strabismic and monocularly deprived kittens to test the hypothesis that binocular connections remain after monocular excitation is ineffective. Finally, stereoacuity will be studied as a function of spatial frequency in humans with normal and abnormal binocular vision. (3) To investigate binocular interaction for unmatched stimuli. Experiments similar to those described above will be conducted using, for one eye, gratings with non-optimal contrast, orientation, or direction to assiss limits of binocular interaction in cats and humans with abnormal binocular vision. (4) To determine the extent of interocular transfer of visual adaptation effects in cats and humans with normal and abnormal binocular vision. By relating neurophysiological and psychophysical observations these investigations should clarify aspects of normal and abnormal binocular function.